Effect of NOx on secondary organic aerosol formation from the photochemical transformation of allyl acetate

Abstract

Smog chamber experiments were conducted to explore the photochemical degradation of allyl acetate (AA) in the presence of SO2 and to assess the role of NOx on the secondary organic aerosol (SOA) formation potential. A one-product gas-particle partitioning absorption model was used to express the formed organic aerosol. The experimental results showed a clear dependence of SOA formation potential on the NOx level. The particle mass concentrations at low NOx conditions (AA/NOx > 3) were commonly higher than those at high NOx conditions (AA/NOx < 3). The SOA yields increased with the increasing NOx concentration under low NOx conditions and decreased with the increasing NOx concentration under high NOx conditions due to the different reaction pathways of RO2 radicals. Gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) analysis suggested that organic nitrates and organic sulfates were formed during photochemistry experiments. Based on detected products, the mechanisms of AA photooxidation were proposed. The results of this study show the different effects of NOx concentrations on promoting and inhibiting aerosol formation, and highlight the pronounced formation of SOA from the photooxidation of AA in polluted environment.